Cellular responses to external factors, such as growth factors, cytokines, and stress conditions, result in altered gene expression. These signals are transmitted from the cell surface to the nucleus by signal transduction pathways. Beginning with an external factor binding to an appropriate receptor, a cascade of signal transduction events is initiated. These responses are mediated through activation of various enzymes and the subsequent activation of specific transcription factors. These activated transcription factors then modulate the expression of specific genes.
The phosphorylation of enzymes plays a key role in the transduction of extracellular signals into the cell. Mitogen activated protein kinases (MAPKs), enzymes which effect such phosphorylations are targets for the action of growth factors, hormones, and other agents involved in cellular metabolism, proliferation and differentiation (Cobb et al., J. Biol. Chem., 1995, 270, 14843). Mitogen activated protein kinases were initially discovered due to their ability to be tyrosine phosphorylated in response to exposure to bacterial lipopolysaccharides or hyperosmotic conditions (Han et al, Science, 1994, 265, 808). These conditions activate inflammatory and apoptotic responses mediated by MAPK. In general, MAP kinases are involved in a variety of signal transduction pathways (sometimes overlapping and sometimes parallel) that function to convey extracellular stimuli to protooncogene products to modulate cellular proliferation and/or differentiation (Seger et al., FASEB J., 1995, 9, 726; Cano et al., Trends Biochem. Sci., 1995, 20, 117).
One of the MAPK signal transduction pathways involves the MAP kinases p38α and p38β (also known as CSaids Binding Proteins, CSBP). These MAP kinases are responsible for the phosphorylation of ATF-2, MEFC2 and a variety of other cellular effectors that may serve as substrates for p38 MAPK proteins (Kummer et al, J. Biol. Chem., 1997, 272, 20490). Phosphorylation of p38 MAPKs potentiates the ability of these factors to activate transcription (Raingeaud et al, Mol. Cell Bio., 1996, 16, 1247; Han et al, Nature, 1997, 386, 296). Among the genes activated by the p38 MAPK signaling pathway is IL-6 (De Cesaris, P., et al., J. Biol. Chem., 1998, 273, 7566-7571).
Besides p38α and p38β, other p38 MAPK family members have been described, including p38γ (Li et al, Biochem. Biophys. Res. Commun., 1996, 228, 334), and p38δ (Jiang et al, J. Biol. Chem., 1997, 272, 30122). The term “p38” as used herein shall mean a member of the p38 MAPK family, including but not limited to p38α, p38β, p38γ and p38δ, their isoforms (Kumar et al, Biochem. Biophys. Res. Commun., 1997, 235, 533) and other members of the p38 MAPK family of proteins whether they function as p38 MAP kinases per se or not.
Modulation of the expression of one or more p38 MAPKs is desirable in order to interfere with inflammatory or apoptotic responses associated with disease states and to modulate the transcription of genes stimulated by ATF-2, MEFC2 and other p38 MAPK phosphorylation substrates.
Inhibitors of p38 MAPKs have been shown to have efficacy in animal models of arthritis (Badger, A. M., et al., J. Pharmacol. Exp. Ther., 1996, 279, 1453-1461) and angiogenesis (Jackson, J. R., et al., J. Pharmacol. Exp. Ther., 1998, 284, 687-692). MacKay, K. and Mochy-Rosen, D. (J. Biol. Chem., 1999, 274, 6272-6279) demonstrate that an inhibitor of p38 MAPKs prevents apoptosis during ischemia in cardiac myocytes, suggesting that p38 MAPK inhibitors can be used for treating ischemic heart disease. p38 MAPK also is required for T-cell HIV-1 replication (Cohen et al, Mol. Med., 1997, 3, 339) and may be a useful target for AIDS therapy. Other diseases believed to be amenable to treatment by inhibitors of p38 MAPKs are disclosed in U.S. Pat. No. 5,559,137, herein incorporated by reference.
Therapeutic agents designed to target p38 MAPKs include small molecule inhibitors and antisense oligonucleotides. Small molecule inhibitors based on pyridinyl imidazole are described in U.S. Pat. Nos. 5,670,527; 5,658,903; 5,656,644; 5,559,137; 5,593,992; and 5,593,991. WO 98/27098 and WO 99/00357 describe additional small molecule inhibitors, one of which has entered clinical trials. Other small molecule inhibitors are also known.
Antisense therapy represents a potentially more specific therapy for targeting p38 MAPKs and, in particular, specific p38 MAPK isoforms. Nagata, Y., et al. (Blood, 1998, 6, 1859-1869) disclose an antisense phosphothioester oligonucleotide targeted to the translational start site of mouse p38b (p38β). Aoshiba, K., et al. (J. Immunol., 1999, 162, 1692-1700) and Cohen, P. S., et al. (Mol. Med., 1997, 3, 339-346) disclose a phosphorothioate antisense oligonucleotide targeted to the coding regions of human p38α, human p38β and rat p38.
There remains a long-felt need for improved compositions and methods for modulating the expression of p38 MAP kinases.